1. Field of the Invention
This invention relates to a mold clamping apparatus for use in molding machines such as injection molding machines, die-casting machines and press molding machines.
2. Background
A mold clamping apparatus for large molding machines is disclosed in Japanese Patent Unexamined Publication No. 82309/1985. The apparatus includes a plurality of clamping cylinders disposed at predetermined positions outside a fixed panel. The piston rods of the respective clamping cylinders are used as tie bars and are inserted into insertion holes arranged on the movable panel such that the movable panel is coupled integrally with the tie bars through engagement with a screw disposed outside the movable panel, so that mold halves respectively mounted on the fixed panel and the movable panel can be clamped together by the clamping cylinders.
In such a mold clamping apparatus, differences in mold thicknesses are accommodated by adjusting the position of engagement between a screw disposed around the front end of each tie bar and a corresponding pair of semi-circular internally threaded chucks disposed outside the movable panel using the clamping cylinder. This requires a long cylinder stroke, entailing problems such as difficulties in maintaining machining accuracy and reasonable cost. It is also difficult to make slight adjustments to account for deviations between screws by hydraulically operating large-diameter pistons, thus requiring cumbersome operations.
In addition, the coupling of the tie bars with their corresponding pairs of chucks through engagement can only be done after the time in which the movable panel is stopped after the mold has been completely closed. Therefore, the time required for coupling is relatively long compared with mold clamping apparatuses of ordinary structure in which such coupling is dispensed with. Thus, this apparatus demands a longer molding cycle due to this additional coupling time.